Ottoite

Chemical formula: Pb₂+₂Te₆+O₅

Ottoite is an extremely rare lead tellurate, occurring as microscopic, colorless crystals with an adamantine luster.

## Characteristics Ottoite is a mineral from the tellurate group, chemically a complex oxide of tellurium and lead. It forms very small, elongated crystals with a prismatic or acicular cross-section, rarely exceeding 0.5 mm in length. They occur as single, isolated crystals or form small, radial and divergent aggregates on the surface of the host rock. Due to its size, it is classified as a micromount mineral, requiring magnification for observation. ## Physical Properties Ottoite crystals are transparent and characterized by a strong, adamantine luster. Their Mohs hardness has not been determined due to their exceptional fragility and small size, which prevent testing. The density calculated based on chemical composition and crystal structure is 7.91 g/cm³, but it has not been empirically measured. ## Colors and Varieties This mineral is colorless to white. No colored varieties or trade names are known. ## History and Name Ottoite was first described in 2011 by a group of mineralogists (Mills, Christy, Jensen, Origlieri, Cannon). Its name honors Dr. James A. "Jim" Otto (born 1951), an American chemist and mineral collector, in recognition of his contributions to mineralogy, especially in the study of minerals from Tombstone, Arizona. ## Uses Ottoite has no industrial application. Its significance is purely scientific and for collectors, being an object of interest for specialists and micromount mineral collectors.

Properties

Luster: Adamantine
Streak: White
Density: 7.91
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Amateur identification of ottoite is practically impossible due to the microscopic size of the crystals. Reliable identification requires advanced analytical techniques such as X-ray diffraction (XRD) and X-ray microanalysis (EDS). Preliminary visual features under magnification include the acicular crystal form, strong adamantine luster, and co-occurrence with other rare tellurates from Tombstone. ## Distinguishing from Similar Minerals Ottoite can be confused with other colorless or white micromount minerals found in the same locality, such as cerussite, paratellurite, or anglesite. Distinguishing it from these minerals based on visual characteristics is unreliable and requires specialized chemical and structural analysis. ## Crystal Forms Ottoite crystallizes in the form of slender, prismatic to acicular crystals, which often form fan-shaped or radial aggregates growing from a single point.

Geological environment

## Genesis Ottoite is a secondary mineral, formed in the oxidation (weathering) zone of hydrothermal deposits rich in tellurium. It forms as a result of the alteration of primary tellurium minerals in the presence of lead under low temperature and pressure conditions, near the Earth's surface. ## Mineral Associations This mineral occurs in association with other secondary tellurium and lead minerals. It is most commonly found in association with quartz, paratellurite, cerussite, dugganite, and chinite. ## Localities The only confirmed locality for ottoite in the world is its type locality - the Baker-Meiklejohn claim (also known as the B and B No. 7 claim) in the Tombstone district, Cochise County, Arizona, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of ottoite specimens, being a micromount mineral, is evaluated by different criteria than for macroscopic specimens. Samples with numerous, well-formed, and sharp crystals, forming aesthetic aggregates, are most highly valued. Minimizing damage and the visual appeal of associated minerals are also crucial. The size of individual crystals, even if sub-millimeter, also affects value. ## Popular Localities All ottoite specimens available on the collector's market come from a single location in the world: the Tombstone area in Arizona, USA. It is an endemic mineral to this locality.

Care and storage

## Cleaning Ottoite specimens are extremely delicate and susceptible to mechanical damage. To remove dust, use only compressed air from a safe distance or a soft camel hair brush, operating with utmost care. Absolutely avoid contact with water, ultrasonic cleaners, and any chemical agents. ## What to Avoid Avoid any physical contact, vibrations, sudden temperature changes, and exposure to chemicals. The crystals are very brittle and can easily break off the matrix. ## Storage It is recommended to store specimens only in specialized, sealed "micromount" boxes that protect against dust, shocks, and mechanical damage. Avoid exposure to direct sunlight, although there is no evidence of its harmfulness.

Sources

IMA Mineral List (CNMNC)